Raise drilling bit

ABSTRACT

A rotary drill for producing a raise bore including a body having roller cutter assemblies arranged to cut the working face of an earth formation so that the plane of an inner portion of the working face inclines downwardly and inwardly towards a pilot hole, and the plane of an outer portion of the working face inclines downwardly and outwardly towards the gage of the raise bore, and the plane of an intermediate portion of the working face extends between the inner and outer inclined portions. This abstract is neither intended to define the invention of the application which, of course, is measured by the claims, nor is it intended to be limiting as to the scope of the invention in any way.

trite Patet Justinian 1 51 Feb.1,1972

[54] RAISE DRILLING BET [21] Appl. No.: 23,583

FOREIGN PATENTS OR APPLICATIONS 1,257,200 2/1961 France ..l75/334 1,092,858 11/1960 Germany 175/53 Primary Examiner-James A. Leppink Att0meyC. M. Kucera [5 7] ABSTRACT A rotary drill for producing a raise bore including a body having roller cutter assemblies arranged to cut the working face of an earth formation so that the plane of an inner portion of the working face inclines downwardly and inwardly towards a pilot hole, and the plane of an outer portion of the working face inclines downwardly and outwardly towards the gage of the raise bore, and the plane of an intermediate portion of the working face extends between the inner and outer inclined portions. This abstract is neither intended to define the invention of the application which, of course, is measured by the claims, not is it intended to be limiting as to the scope of the invention in any way.

7 Claims, 2 Drawing Figures PATENTEUFEB 1m 3.638.740

DAN B. JusTMA/v INVENTOR.

ATTORNEY RAISE DRILLING BIT BACKGROUND The present invention relates to earth boring drill bits, and particularly to drill bits for the drilling of raises extending from mine galleries or shafts at one level to galleries or shafts at other levels.

It is now common practice to drill raises from a lower level along a pilot hole with drilling bits having roller cutters arranged to cut the formation in steps. For example, such a bit may have in steps, inner cutters, intermediate cutters and outer cutters, with the inner cutters cutting a bore adjacent the pilot hole and vertically in advance of the intermediate and outer cutters. Thus, during the drilling operation, there is produced a gage surface for the bore cut by the inner cutters, and a gage surface for each of the bores produced by the intermediate and outer cutters. The earth formation at the juncture of the wall or gage of a bore with the working face is difficult to dnill since the working face and gage wall mutually support each other so that the force required to efiect drilling of the formation in this corner is greater than elsewhere on the working face of the formation. At the same time, the gage of the bore must be maintained. Drilling raises with such stepped cutter arrangements requires high torque, and such arrangement also contributes to early cutter wear necessitating replacement thereof.

SUMMARY This invention relates to a raise bore drill having roller cutters arranged so that only a single bore hole gage surface is produced: that of the desired diameter of the raise bore. The working face produced on the formation between the pilot hole and the gage wall is substantially contiguous, rather than in a series of vertical steps. A vertical section through one-half of the working face (from the pilot hole to the gage wall) would show the surface of the working face to be in a form resembling a section through an inverted, shallow dish. Thus, the drill of the invention requires less torque to operate than comparable stepped drills resulting in less wear on the drill bit and attendant parts. Since the intermediate cutters in effect lead" the inner and outer cutters during the raise boring operation to cut the inverted dish shape as just described, a substantial stabilizing influence is imparted to the drill bit resulting in a smooth operating raise drilling bit.

An object of the present invention is to provide a new and improved raise drill to cut a substantially contiguous working face on the formation being drilled so that only a single bore hole gage surface is produced.

Another object is to provide a new and improved raise drill to cut a configuration on the working face of the formation which tends to stabilize the drill during the operation thereof to provide smoother operation of the drill, at less torque, which drill has extended life and provides improved drill footage.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of a raise bore having a raise drill shown in elevation and partly in section located therein with portions of the cutting structure moved into the plane of the paper to illustrate the manner of cutting the entire working face being drilled.

FIG. 2 is a plan view of the raise drill.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in the drawings, the raise drill includes an alloy steel upper plate 11 and a lower plate 12 welded to a generally cylindrical steel drive stem 13 to form a drill head or body. Steel gussets 14 may be welded between the drive stem 13 and the upper plate 11 for additional strength. The drive stem 13 extends upwardly into a pilot hole 15 in the earth formation and may be attached by means of a threaded connection 16 into a drill stern (not shown).

A cutter assembly 17 is secured in saddle mounting 18 to form an outer cutter assembly 19. A cutter assembly 17 is secured in saddle mounting 20 to form an intermediate cutter assembly 21. The saddle mountings 18 and 20 may be suitably secured to the bit head or body as by welding.

The cutter assembly 17 is mounted between support 22 and drive stem 13 to form an inner cutter assembly 23. The cutter assembly 17 comprises a roller cutter 230 which may be made of alloy steel and in the cutter shown in FIGS. 1, hard metal inserts 24 which may be made of tungsten carbide or the like are pressed into the cutter 23a to form cutting elements to drill the formation being encountered. If desired, the cutter may be provided with steel teeth which are milled into the cutter. Such cutting elements are well known in the art.

The cutter assembly 17 shown in FIG. I is supported between support 22 and drive stem 13 by means of a pin 25 which is fastened to the support 22 by means of a bolt 26. The inner end of the pin 25 is inserted into a socket 27 in the drive stem 13.

The roller cutter 23a is rotatably mounted on a journal 28 on roller bearings 29 and 30 and ball bearings 31 in suitable bearing races.

The cutter assemblies 17 are similar and they may be mounted in saddle 18 on a pin 32 and secured to the saddle by means of a bolt 33. In similar fashion, the cutter assembly 17 may be mounted in saddle 20.

The drive stem 13 may have wrench flats 34 to facilitate connecting or disconnecting the threaded connection 16 into a drill stem (not shown). The drive stem 13 may also have secured to its surface wear-resistant pads 35 to alleviate wear of the drive stem 13.

The art of earth boring known as raise drilling comprises the drilling of a relatively small pilot hole on a downward pass, followed by enlargement of the hole to a predetermined raise diameter by rotating and raising the drill along the pilot hole to form a raise bore between a lower level and an upper level in a single upward pass, the drill being rotated from above and guided by the pilot hole. The cuttings produced during such drilling operation are allowed to fall to the lower level.

With the pilot hole 15 formed, the raise drill I0 is connected by means of the threaded connection 16 of the drive stem 13 into a drill stem (not shown). Raise bores are usually 36 inches in diameter or more, and in the embodiment described, the raise bore 36 may have a diameter of approximately 48 inches and the pilot hole 15 may have a diameter of about 9 to 11 inches. Such drill may weight approximately 5,000 pounds. As the raise drilling operation is commenced by rotation of the drill stem by a drilling rig, the bit may be rotated approximately 10 to 40 rpm. while the rig exerts an upward pull on the bit of approximately 150,000 to 250,000 pounds. As drilling progresses sections of the drill stem which may comprise cylindrical or tubular members approximately 5 feet long are progressively uncoupled at the upper level and the raise is completed by progressively rotating and lifting the drill stem and the raise drill.

As shown in FIG. I at 37, the intermediate cutter assembly 21 cuts the formation in a plane ahead of those produced by the inner cutter assembly 23 and the outer cutter assembly 19 whereby a cross section of the working face of the formation between the pilot hole 15 and the wall of the bore 36 resembles a cross section through an inverted dish.

In the example shown, the plane 37 of the working face produced by the intermediate cutter assembly 21 is substantially horizontal. An inner conical surface 38 is cut adjacent the pilot hole 15 by the inner cutter assembly 23, the plane of which inclines downwardly and inwardly and is substantially contiguous with the plane 37. An outer conical surface 39 adjacent the wall of the bore hole 36 is cut by the outer cutter assembly 19, the plane of which inclines downwardly and outwardly and is, substantially contiguous with the plane 37. Such cutter assembly arrangement serves to cut in one pass the entire working face of the formation from the pilot hole I5 to the wall of the bore 36 whereby only a single gage portion needs to be cut: the gage of the bore hole 36. Since only one gage portion is cut, the drill of the invention requires less torque for drilling and affords faster and smoother drilling with less wear on the cutters and attendant parts.

When the drill first contacts the formation on the upward pass, the intermediate cutter assembly 21 strikes the formation before the inner and outer cutter assemblies 23 and 19 so that the starting diameter of the face being cut is smaller than the diameter of the final bore thus providing easier and smoother starting of the drill into the formation and imparting enhanced stability to the drill during the start of such drilling operation. After the drill is fully engaged in the formation, the inner and outer conical surfaces 38 and 39 and the gage of the bore 36 provide stability for the drill.

As previously discussed, the earth formation at the juncture of the wall of the bore hole 36 with the outer conical surface 39 of the working face is difficult to drill, and in the example shown, four outer cutter assemblies 19 are provided to cut this annular track while only two inner cutter assemblies 23 and two intermediate cutter assemblies 21 are provided to cut the balance of the working face.

As shown, the outer cutter assembly 19 is arranged so that the outer conical portion 39, inclined approximately 10 to 30 from the horizontal, is produced and the inner cutter assembly 23 is arranged so that the inner conical portion 38, inclined approximately l to 25 from the horizontal, is produced. The intermediate portion 37 produced by the cutter assemblies 21 is approximately horizontal and extends between portions 38 and 39 to form a substantially contiguous surface across the entire working face.

The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape and materials as well as in the details of the illustrated construction, may be made within the scope of the appended claims without departing from the spirit of the invention What is claimed is:

l. A rotary drill for producing a raise bore along a pilot hole in an earth formation having a stem member with a plate member secured thereto in a plane normal thereto to define a body, a plurality of roller cutter assemblies including inner cutters and intermediate cutters and outer cutters, each of said inner and intermediate and outer cutters being mounted independently of one another upon separate supporting members secured to and carried by said plate member, said inner cutters being mounted on substantially horizontally disposed supporting members secured to said stem member and plate member, each cutter assembly arranged on said plate member to cut the working face of the earth formation surrounding said pilot hole with a plane of the inner portion of the working face being inclined downwardly and inwardly towards the pilot hole and the plane of the outer portion of the working face being inclined downwardly and outwardly towards the gage of the raised bore with the plane of an intermediate portion of the working face extending between said inner and outer portions to produce a substantially contiguous working face.

2. A rotary drill as set forth in claim 1 wherein said inner cutters are interposed between certain of said outer cutters and said intermediate cutters are interposed between certain other cutters of said outer cutters.

3. A rotary drill as set forth in claim 1 wherein said outer cutters are each mounted on an axis and inclined towards said plate member.

4. A rotary drill as set forth in claim 1 wherein said plate member is of annular configuration with the cutter assemblies being mounted thereon in diametrically disposed pairs.

5. A rotary drill according to claim 1, wherein the plane of the outer portion of the working face is inclined downwardly between approximately 10 to 30 from a horizontal plane.

6. A rotary drill according to claim 1, wherein the plane of the inner portion of the working face is inclined downwardly approximately 10 to 25 from a horizontal plane.

. A rotary drill according to claim 1, wherein the entire working face of the formation is cut in one pass and only a single gage wall portion is produced, the said gage being that of the desired raise bore. 

1. A rotary drill for producing a raise bore along a pilot hole in an earth formation having a stem member with a plate member secured thereto in a plane normal thereto to define a body, a plurality of roller cutter assemblies including inner cutters and intermediate cutters and outer cutters, each of said inner and intermediate and outer cutters being mounted independently of one another upon separate supportiNg members secured to and carried by said plate member, said inner cutters being mounted on substantially horizontally disposed supporting members secured to said stem member and plate member, each cutter assembly arranged on said plate member to cut the working face of the earth formation surrounding said pilot hole with a plane of the inner portion of the working face being inclined downwardly and inwardly towards the pilot hole and the plane of the outer portion of the working face being inclined downwardly and outwardly towards the gage of the raised bore with the plane of an intermediate portion of the working face extending between said inner and outer portions to produce a substantially contiguous working face.
 2. A rotary drill as set forth in claim 1 wherein said inner cutters are interposed between certain of said outer cutters and said intermediate cutters are interposed between certain other cutters of said outer cutters.
 3. A rotary drill as set forth in claim 1 wherein said outer cutters are each mounted on an axis and inclined towards said plate member.
 4. A rotary drill as set forth in claim 1 wherein said plate member is of annular configuration with the cutter assemblies being mounted thereon in diametrically disposed pairs.
 5. A rotary drill according to claim 1, wherein the plane of the outer portion of the working face is inclined downwardly between approximately 10 * to 30* from a horizontal plane.
 6. A rotary drill according to claim 1, wherein the plane of the inner portion of the working face is inclined downwardly approximately 10* to 25* from a horizontal plane.
 7. A rotary drill according to claim 1, wherein the entire working face of the formation is cut in one pass and only a single gage wall portion is produced, the said gage being that of the desired raise bore. 